Introduction

16k memory (12 k available for BASIC, 2k with graphics enabled), case
very similar to that of the old C64 ("breadbox"), dark gray color.

Plus/4

64k memory (60 k available for BASIC, 50k with graphics enabled), the
shape of the case is similar to that of the C116, but somewhat larger
and the Plus/4 has a "real" keyboard. Builtin software: Spreadsheet,
word processor. Builtin ACIA (6551) but without real RS232 driver
chips (Commodore did a lot things like this), so an external adapter
providing the drivers was needed.

There are some more models, but the three described above are the only ones
actually marketed. It seems that the C116 was only sold in Europe.

Hard- and Firmware

All machines have the same hardware with some minor differences (6551 missing
in C116/C16, different memory size and use of different memory chips, two
additional ROMs in the Plus/4). Kernal and BASIC roms were identical, which
means that an external ACIA chip added to the C16/C116 is supported by the
kernal.

The 264 series had BASIC version 3.5 which is somewhat confusing, since it has
more commands than the BASIC version of the old PETs (BASIC 4.0). BASIC 3.5
had all the disk commands of BASIC 4.0, but also support for graphic and
sound. It is comparable to the BASIC 7.0 of the C128 but lacks the extensions
for structured programming.

Graphic and sound was done by a highly integrated chip named "TED". Some of
the software was called after this chip, for example the builtin machine
language monitor was named "TEDMON". The TED supports text mode with 25 rows
and 40 columns plus colors. Text mode is similar to that of the C64 but has
additional 3 luminance bits for each color cell allowing 121 colors total (the
odd number results from the fact that the eight luminances for black do not
differ). Graphics mode was comparable to that of the C64 (320*200 high res and
160*200 multicolor mode) with the difference that the luminance bits do also
work in this modes giving more total colors. The TED does not support sprites
and the sound capabilities are far inferior to that of the C64.

BASIC 3.5 has support for high resolution graphic (320*200 pixel), but
switching into graphics mode meaned that the available memory was decreased by
10K (8K for the bitmap and 2K for the video matrix), leaving just 2K for BASIC
on the C16/C116. This made these models pretty useless without a memory
extension. But as said above, the kernal is identical, so added memory (for
example by replacing the memory chips and soldering some additional lines or
by an expansion card) is supported by the kernal and by BASIC.

The 264 series had a 7501 CPU (8501 on later models) that was software
compatible to the NMOS 6502 (what else would you expected from Commodore?).
The CPU had a clock frequency of 1.78 MHz, so it is faster than the C64 or the
old PETs, even if the CPU is stopped here and then by the TED.

Memory map

The memory map of the 264 series is similar to the C64 but somewhat more
elaborated, and the BASIC intepreter does support bank switching, so most of
the RAM is available for BASIC.

On a machine with 64K RAM (a Plus/4 or an extended C16 or C116) the lower 32K
were always RAM. The high 32K could be switched between RAM or ROM. When ROM
is switched in, the range is subdivided into two 16K blocks, and in each of
these blocks one out of four ROMs could be banked in. Unfortunately it is not
possible to select a ROM in one of both 16K blocks and RAM in the other, a
configuration that would give 48K of RAM plus one ROM (the kernal for
example). This makes it somewhat difficult to write larger programs without
banking.

The additional software of the Plus/4 was built into two ROMs that are banked
in when the software is started.

Programming

The 264 series machines are very nice from a programmers view, at least when
equipped with 64K memory. The only drawback is the banking needed for larger
programs. BASIC 3.5 is very comfortable, and the builtin machine language
monitor (that even has a disassembler and a line assembler) makes writing
short programs very easy.

There was a complete kernal disassembly available in a book sold from
Markt&Technik in Germany (Commodore Sachbuch), it was useful and very well
done.

Photo safari

Larger numbers of the C16 and the C116 were sold by Aldi, a german
discounter. The box did contain the computer, a datasette, an extra
BASIC handbook and was sold as "BASIC learning course".

The picture to the left is a view of another box. This one was sold by
Vobis in the old days. As usual, clicking on the picture will give a
larger one, and clicking on the larger picture will give the picture
in original size.

A front view of the C116. As you can see, no one would really like to
work this this keyboard. The C116 was about 50.- DM (25 Euro) cheaper
than the functionally identical C16 in the time when both were sold.
For this money you got mostly the better keyboard of the C16.

Click on the picture for a larger view.

Here is a rear view of the C116. From left to right: The power connector; a
reset switch (yes, the C116 had one!); the connections for the serial IEEE bus
and the datasette; expansion port; two joystick ports and the video output.

As you can see, the datasette and joystick connectors differ from the C64 and
VIC 20 (which had the same joystick connectors as the Atari video consoles).
This was a major problem, and there was only one joystick (model T-1341, sold
under the Commodore brand) that had this connector. For all others, expensive
adaptors were needed.

A view from the top. The rectangle on the right side with the arrow
shapes on it are the cursor keys. As you can see, the 264 series
machines had 4 function keys as all other Commodore home computers. F8
(that is, Shift-F7) is labeled as "Help". This key made a BASIC line
with an error flash - something that was more annoying than helpful,
since the flashing couldn't be stopped.

Left view of the case (hope this doesn't get boring). The 264 series
machines had a RF modulator builtin like the C64 (and unlike the
VIC20). As usual, there were NTSC and PAL machines available - or at
least NTSC and PAL TED chips. I do not know if there is really a NTSC
C116, I've been told that these machines were only sold in Europe.

A first view into the case. The machine is heavily shielded inside, so the
mainboard itself is mostly invisible for now. A closer look at the shielding
reveals that it is bent somewhat (lower part, right half). This is because the
machine has a memory expansion installed. The two replacement memory chips
have additional sockets installed which did not fit exactly into the shielding
case. The flat wire in the top left is the connection to the keyboard, which
is mounted in the top of the case.

A view into the case with shielding and top removed. Compared to the
C64, the 264 series machines do contain a smaller number of chips,
since the TED has the functionality of the VIC, the SID and part of
the CIAs. The three bigger chips on the right side (marked with yellow
dots) are kernal and BASIC ROM and a PLA used as an address manager.
In the center, the CPU (smaller chip, yellow dot) and the TED (largest
chip, white dot). The chip with a yellow dot on the left side of the
TED is a 6529, an eight bit I/O port. The sockets of the memory
expansion are now clearly visible.

Last one: The following scans are from an advertisement sheet describing all
members of the 264 family. The text is in german. Click on any of the images
for a larger view.